Drilling a well hole typically involves drilling to a certain depth with a drill bit mounted on a drill string, then removing the drill string from the hole in order to case the hole. The pipe or casing is driven into the hole by repeated impact. Generally it is not desirable to drill too far down before casing the hole, as the sides of an uncased hole may be susceptible to collapse and to leaks from the surrounding formation. The drill-then-case process has to be repeated several times to produce a deep hole. Drilling a hole can therefore be a time-consuming process. To maximize production and profits, it is necessary to minimize the time spent completing a hole.
Advancing a pipe into the earth usually requires costly, heavy and cumbersome equipment, including a massive driving device to either develop the impact energy or to transmit impact energy to the pipe or casing. The device must be securely mounted on a drill rig, necessitating modifications to the drill rig to be able to handle the driving device. Existing driving devices are generally large and require additional equipment for their operation, such as hydraulic pumps or air compressors. Once installed on a rig, a driving device is usually difficult to remove.
U.S. Pat. No. 3,895,680 to Cook discloses a hammer by which a pipe may be driven into the ground, without any type of drilling mechanism. A heavy, hollow ram is raised by a pair of air cylinders mounted on the outside of the ram. The ram travels downward transmitting a blow to the pipe being installed. The force of the blow is determined by the weight of the ram. The system requires an external source of compressed air and a complex control system. The force of the impact is not adjustable, as might be desired when casing in softer or less dense strata.
Drilling equipment or drilling rigs come in various sizes, with different hoisting systems and various tower configurations. A common approach is to modify the tower and equipment to adapt to the driving device. Due to the size and operational methods, several drilling rigs have towers and hoisting capabilities, which are too small to adapt to the installation of conventional casing driving equipment.
It is known in the art to case the hole while drilling as a means of improving the speed and efficiency of the drilling process. The present invention relies on a simple casing driver which is small, easy to handle and adaptable for various drilling rigs, in contrast to many of the other prior art devices, which rely on heavy, cumbersome machinery and require special handling procedures. Further, the prior art devices, generally being controlled by hydraulic or pneumatic means, require an independent source of power, and controls for that power.
U.S. Pat. No. 3,833,072 to Back illustrates a drilling machine including a casing-driving element. While the device is intended to be relatively low weight and portable, it still requires an external source of hydraulic pressure, and a complex intermittent pressure regulation system to operate the driver.
U.S. Pat. No. 4,232,752 to Hauk et al. employs a lightweight, short stroke annular piston, while increasing the rate of impact on the casing. Each individual impact is low energy, which is compensated by the increased frequency of the impacts. As in Cook, the piston is pneumatically driven. The driver further includes a complex set of valve chambers and passages to maximize the efficiency of pneumatic system.
In U.S. Pat. No. 6,029,757, Anderson et al. disclose a casing hammer assembly containing a central aperture surrounding a drill string. To drive the casing, a reciprocating hammer strikes an impact anvil surrounding the central aperture. Anderson et al. manage to avoid the use of pneumatic or hydraulic means to operate the hammer, instead reciprocating the hammer by use of an eccentric arrangement. This arrangement involves sprockets and chains driven by a rotating shaft and sleeve. The shaft itself is driven by a motor, which requires its own power source. However, the relatively complex arrangement of chains and sprockets between the shaft and the hammer leaves the entire assembly more vulnerable to failure. The use of a separate motor results in an additional part that could fail or need maintenance. Further, the entire assembly is suspended from the drilling rig above the casing pipe by a set of cable pulleys and cables, which could cause problems with the storage of the driver when not in use.
U.S. Pat. No. 6,371,209 to Allyn et al. discloses a device for the removal of casing. The device disclosed by Allyn et al. relies upon an existing pneumatic hammer drill for it to operate, and a source of power. Allyn et al. rotates the pipe or casing to install it, which requires that the ends of the each pipe be threaded.
It is one object of the invention to provide a new method of advancing pipe into the earth.
It is a further object of the invention to provide a method of advancing pipe without the need for air or hydraulics to operate the device.
It is an object of the invention to provide a driving device which is versatile, in that it may be used on virtually any existing drill rigs without modification to the drill rigs in order to use the driver.
It is a further object of the invention to provide a driving device which is easily attached to a string of drilling tools being rotated by a drilling rig or rotating device.
It is a further object of the invention to provide a driving device which, once attached to the drill string, can be selectively operated, allowing the drill crew to drill without hammering, yet without physically removing the driver from the drill string.
These and other objects of the invention will be appreciated by reference to the summary of the invention and to the detailed description of the preferred embodiment that follow. It will be appreciated that all of the foregoing objectives may not be satisfied simultaneously by the preferred embodiment or by each of the claims.